Dan Kloeffler with video and details on the origins of MAD’s fold-ins, and one that didn’t see the light of day.
That idea was born when Jaffee saw fold-outs in magazines such as National Geographic and Life and, in typical MAD fashion, decided to do the opposite, creating the fold-in. A single image appears on the inside back cover along with a question. The reader folds the page in to reveal another image and the answer to the question. Thinking it was a “one-shot” gag, Jaffee was surprised when his editor demanded a fold-in for the next issue and it quickly became a regular feature.
I grew up on MAD Magazine (which accounts for the warped sense of humor). The video in the article displays the fold-in that didn’t run.